Effect of a baited trap on the foraging movements of juvenile western rock lobsters, Panulirus cygnus George

1988 ◽  
Vol 39 (2) ◽  
pp. 185 ◽  
Author(s):  
P Jernakoff ◽  
BF Phillips
Keyword(s):  
Patch Reefs ◽  
Foraging Range ◽  
Catch Rates ◽  
Panulirus Cygnus ◽  
Foraging Movements ◽  
Individual Patch

The influence of a commercial trap on the foraging movements of juvenile P. cygnus was determined by tracking animals to which electromagnetic tags had been attached. Catch rates were low. Tagged lobsters were caught on eight occasions; on 14 occasions, tagged lobsters visited the trap and stayed for several hours during the night, but left by morning. The greatest distance travelled by a lobster from down stream to the baited trap was 120 m. On 19 occasions lobsters upcurrent from the trap passed as close as 20 m without going to the trap, although other lobsters as far away as 75 m upcurrent visited the trap. Previous tracking records of individuals foraging upcurrent of the trap suggest that these lobsters' visits may have been due to the trap's location within their foraging range rather than to detection of the bait. Present trapping techniques used to estimate the densities of juvenile lobsters on individual patch reefs may be biased because lobsters on neighbouring reefs as far away as 120 m could be attracted to the baited trap. The present results also suggest that some lobsters may leave the traps before sunrise, and that traps set closer than 120 m apart may fish competitively for the same individuals.

scholarly journals The orientation and migratory dynamics of the western rock lobster, Panulirus cygnus, in Western Australia

2014 ◽  
Vol 71 (5) ◽  
pp. 1052-1063 ◽  
Author(s):  
Simon de Lestang
Keyword(s):  
Large Scale ◽  
Economic Benefits ◽  
Rock Lobster ◽  
Commercial Catch ◽  
Breeding Grounds ◽  
Mean Size ◽  
Catch Rates ◽  
Panulirus Cygnus ◽  
The Impact ◽  
Oceanic Currents

Abstract Large-scale migrations are known to occur in numerous species, and in the case of the Western Rock Lobster, Panulirus cygnus, result in juveniles moving from nursery areas into deeper offshore breeding grounds. In 2008 the Western Rock Lobster fishery reduced harvest rates to increase legal and spawning biomass throughout the fishery, which also allowed greater numbers of lobsters to migrate. Increased lobster migration could potentially reduce biomass in some areas, thus adversely impacting commercial catch rates. Over 20 000 tag–recaptured lobsters were analysed to determine the dynamics underlying migration in this species and to assess the impact reduced harvest rates may have had on catches. This study showed that P. cygnus migration was associated with body size and water depth, and that magnetism and oceanic currents appear to be the most likely guideposts used for orientation. Size at migration varied in a constant fashion along the coast, being larger towards the southern end of the fishery and smallest at the offshore Abrolhos Islands. During the migration period, up to 50% of lobsters at their mean size of migration moved from coastal areas out towards deeper waters (>40 m), whereas <15% of those in deeper water at the same size moved significant distances northward. This behaviour appears to be contranatant, counteracting the downstream redistribution of larvae after their 9–11 month larval life. Reduced harvest rates and catches being focussed onto higher valued sedentary lobsters have allowed more lobsters to migrate. However, the numbers moving between management areas are relatively small, with the biological and economic benefits of fishing at a reduced exploitation rate outweighing losses to catches.

Development of an individual-based tag recapture model to benchmark biomass and harvest rates in an iconic lobster fishery

2021 ◽  
Author(s):  
Simon de Lestang ◽  
John Hoenig ◽  
Jason How
Keyword(s):  
Stock Assessment ◽  
Size Composition ◽  
Dynamics Model ◽  
Maximum Economic Yield ◽  
Current Assessment ◽  
Wide Scale ◽  
Lobster Fishery ◽  
Catch Rates ◽  
Panulirus Cygnus ◽  
Strong Agreement

The West Coast Rock Lobster Managed Fishery (WCRLMF) moved from input to output controls in 2010. This change affected the relativity of fishery-based data sources (e.g., catch rates and landed size composition), making the assessment of the fishery problematic. A novel examination of the stock dynamics was required to ensure the robustness of the stock assessment and associated management arrangements. This study derived estimates of current biomass levels and harvest rates from the release of over 60,000 tagged western rock lobsters (Panulirus cygnus). A “Brownie” tag-recapture (BTR) model was initially implemented to provide an assessment on a fishery-wide basis. Estimates from this were compared to those derived from a novel purpose-built tag-recapture individual-based model (IBM) that accounted for sex, size, month, and location-specific changes in catchability. The two models produced similar estimates on a fishery-wide scale—harvest rate (HR 0.26 vs 0.30, respectively) and legal-sized biomass (about 24,500 vs 20,735 t, respectively)—while the IBM also provided estimates on a far finer spatial and temporal scale. Both models indicate that the WCRLMF is currently in a very sustainable condition and is being fished at a rate below maximum economic yield (HRmey is about 0.39). These findings were in concert with estimates derived for this fishery based on two separate catch-rate based population models, an integrated population model and a biomass-dynamics model. Such strong agreement among all models provides great certainty in the current assessment and management of this important marine resource.

Seasonal and annual foraging movements of little penguins from Phillip Island, Victoria

1999 ◽  
Vol 26 (6) ◽  
pp. 705 ◽  
Author(s):  
M. Collins ◽  
J. M. Cullen ◽  
P. Dann
Keyword(s):  
Breeding Season ◽  
Prey Species ◽  
Breeding Period ◽  
Similar Distribution ◽  
Breeding Colony ◽  
Foraging Range ◽  
The North ◽  
Foraging Movements ◽  
North And South

Little penguins, Eudyptula minor, from a breeding colony on Phillip Island, Victoria were radio-tracked at sea during incubation, chick-rearing and non-breeding periods from 1991 to 1993. Their locations, which we have assumed to reflect foraging movements, varied according to season and breeding activities, and there were marked differences from year to year. Duration and distance of trips ranged from single day-trips a few kilometres from Phillip Island, typically during the breeding season, to longer trips outside the breeding season up to 500 km away lasting more than a month, but 95% of all birds located were within 20 km of the coast. In the breeding season foraging trips averaged 4.4 days during incubation compared with 2.1 days when there were chicks in the nest; in the non-breeding period foraging trips took 5.2 days on average. The duration of trips for adults feeding chicks increased with the age of the chicks. Birds from nests on the north and south sides of Phillip Island differed in their use of areas close to the island, but showed a similar distribution on more distant trips. The location of foraging trips is discussed in relation to information on the abundance of prey species of fish within the foraging range of the birds.

scholarly journals Spring foraging movements of an urban population of grey-headed flying foxes (Pteropus poliocephalus)

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Wayne S J Boardman ◽  
David Roshier ◽  
Terry Reardon ◽  
Kathryn Burbidge ◽  
Adam McKeown ◽  
...  
Keyword(s):  
South Australia ◽  
Flying Foxes ◽  
Location Data ◽  
Forage Plants ◽  
Foraging Range ◽  
Mobile Species ◽  
Pteropus Poliocephalus ◽  
Corymbia Citriodora ◽  
Port Jackson ◽  
Foraging Movements

Abstract Flying foxes provide ecologically and economically important ecosystem services but extensive clearing and modification of habitat and drought combined with the planting of commercial and non-commercial trees across various landscapes, has meant flying foxes in Australia are increasingly seeking foraging resources in new areas. In 2011, grey-headed flying foxes formed a camp in Adelaide, South Australia, outside their previously recorded range. We used global positioning system telemetry to study the movements and foraging behaviour of this species in Adelaide in spring (September to November) 2015. High-frequency location data were used to determine the foraging range and the most frequently visited foraging sites used by each bat which were ground-truthed to identify forage plants. A total of 7239 valid locations were collected over 170 nights from four collars. Despite being a highly mobile species, the mean core foraging range estimate was only 7.30 km2 (range 3.3–11.2 km2). Maximum foraging distance from the camp in the Botanic Park was 9.5 km but most foraging occurred within a 4-km radius. The most common foraging sites occurred within the residential area of Adelaide and included introduced forage plant species, Lemon-scented gum (Corymbia citriodora) and Port Jackson fig (Ficus rubiginosa). Other observed movement activities included dipping behaviour on inland and marine waters and travel across flight paths around Adelaide airport. Our findings suggest that urban habitats in Adelaide provide sufficient foraging resources for grey-headed flying foxes to use these areas exclusively, at least in spring. This creates substantial opportunities for bats to interact with humans and their infrastructure.

Testing collector designs for commercial harvesting of western rock lobster (Panulirus cygnus) puerulus

2001 ◽  
Vol 52 (8) ◽  
pp. 1465 ◽  
Author(s):  
Bruce F. Phillips ◽  
Roy Melville-Smith ◽  
Yuk Wing Cheng ◽  
Mark Rossbach
Keyword(s):  
Published Data ◽  
Rock Lobster ◽  
Different Depths ◽  
New Moon ◽  
Catch Rates ◽  
Highly Correlated ◽  
Carry Over ◽  
Panulirus Cygnus ◽  
Do So ◽  
Commercial Harvesting

We have (i) tested modified western rock lobster sandwich collectors at different depths and distances offshore (ii) tested different collector designs (iii) examined the effect of collector size, and (iv) tested the effect of frequency of servicing the collectors. The only catches recorded in the onshore-offshore trials were on gear set at the inshore site (depths <5 m). Published data from the 1970s on the effect on catches of collector arrays and locations were reexamined with a general linear model. The analysis revealed marginally significant corner and layer effects, carry-over effects, and square-of-time effects. Five collector designs were therefore set in the shallows, two of which had replicates of three different sizes, and were checked over four lunar months during peak settlement. Sandwich collectors had significantly better catch rates than others (P <0.001), and settlement rates were highly correlated with collector dimensions (r = 0.72). Daily servicing for seven days around the time of new moon yielded catches 170% higher than those from a single monthly servicing (P <0.001). Results indicate that tests for collectors must take into account corner, carry-over, neighbour, and layer effects and that to do so they must be set out in an array and repositioned after each sampling.

Relationship Between Indices of Juvenile Abundance and Recruitment in the Western Rock Lobster (Panulirus cygnus) Fishery

1986 ◽  
Vol 43 (11) ◽  
pp. 2131-2139 ◽  
Author(s):  
N. Caputi ◽  
R. S. Brown
Keyword(s):  
Moving Average ◽  
Monitoring Program ◽  
Catch Rate ◽  
Regression Coefficients ◽  
Multiple Correlation ◽  
Juvenile Abundance ◽  
The Status ◽  
Catch Rates ◽  
Panulirus Cygnus ◽  
Index Of Abundance

Indices of abundance of 3- and 4-yr-old juvenile western rock lobsters (Panulirus cygnus) were used to determine the status of the stocks between the puerulus stage and subsequent recruitment to the fishery. These indices were based on logarithmically transformed catch rate data of undersize lobsters obtained from a monitoring program which commenced in 1971–72. The juvenile indices were determined from regression coefficients associated with the factor "year", adjusted for other factors, e.g. location, month, depth, soak time, which affect juvenile catch rates. A revised index of recruitment was based on logarithmically transformed catch rates, in depths up to 18 m. A 7-d moving average was used to smooth out daily fluctuations to enable the "best" 60-d catch rate over the period of recruitment to the fishery (November–January) to be determined so that differences in the time of recruitment may be taken into account in quantifying the level of recruitment. This index is compared with a previous recruitment index based on total catch divided by total effort during November–December. The relationships between the abundance indices of 3- and 4-yr-old male juveniles and the recruitment index resulted in correlations of 0.95 and 0.93, respectively, from the log–log analyses of 11 year-classes with a multiple correlation of 0.97 when the 3- and 4-yr-old indices were used in a multiple regression. These indices provide an independent method to support or modify the prediction of recruitment based on an index of abundance of settling puerulus (aged 9–11 mo) obtained 4 yr before they recruit into the fishery.

Fish community structure, habitat complexity, and soundscape characteristics of patch reefs in a tropical, back-reef system

2019 ◽  
Vol 609 ◽  
pp. 33-48 ◽  
Author(s):  
RP Lyon ◽  
DB Eggleston ◽  
DR Bohnenstiehl ◽  
CA Layman ◽  
SW Ricci ◽  
...  
Keyword(s):  
Community Structure ◽  
Habitat Complexity ◽  
Fish Community ◽  
Back Reef ◽  
Fish Community Structure ◽  
Patch Reefs ◽  
Reef System

Physiography, Ecology, and Sediments of Two Bermuda Patch Reefs

1971 ◽  
Vol 79 (6) ◽  
pp. 647-668 ◽  
Author(s):  
Peter Garrett ◽  
Donald L. Smith ◽  
Augustus O. Wilson ◽  
David Patriquin
Keyword(s):  
Patch Reefs
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